Respiratory System

 

Introduction

Learn all about the human respiratory system. 

There are 2 parts to the learning objectives, each learning objective contains information and questions to help prepare you for the upcoming lesson.

 

 

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Part 1 - Describe the function, location and structure of the respiratory system.

Identify the organs of the Respiratory system

Organs of the Respiratory system

The respiratory system consists of the noselungsdiaphragm and the air passages, such as the trachea, which connect them.

The respiratory system is the body’s breathing equipment.

Similar to the digestive system, it takes substances from outside the body (gases, particularly oxygen), circulates them through the body to cells and tissues, then excretes the excess and waste.

Oxygen is the respiratory system’s ‘food’ and carbon dioxide is its ‘waste’.

Breathing is the most fundamental action of the human body; we cannot live without it for more than a couple of minutes.

  • Pharynx
  • Trachea
  • Larynx
  • Bronchus
  • Diaphragm

Match the functions of Respiratory system

Breathing rate

The normal breathing rate is 12 to 15 breaths per minute although this may increase during exercise and stress, and decrease during sleep.

Breathing takes place rhythmically, with insipration lasting for about two seconds and expiration for approximately three seconds.

  • Olfaction
    send impulses for the sense of specialised nerve endings embedded in the nasal cavity ell to the brain.
  • Homeostasis
    by maintaining oxygen levels in the blood and through the elimination of wastes such as carbon dioxide and heat.
  • Exchange of gases
    oxygen and carbon dioxide exchange
  • Speech
    the vocal cords in the larynx aid in producing speech.

Nose

Structure
The nose is made of cartilage and two nasal bones. It is covered with skin, both inside and out and lined with a mucous membrane that is ciliated i.e. it has microscopic hairs.

The two nostrils lead into a bony nasal cavity, which has two chambers, divided by a nasal septum. The septum is made of cartilage. Thus the outside of the nose which we can see, is mostly made of cartilage whereas the inside of the nose is mostly made of bone.

The nasal cavity connects to the paranasal sinuses, hollow spaces inside the bones surrounding the nose which are full of air and are also lined with mucous membrane.

Functions:

  • to work as the organ of smell
  • to moisten and warm the air entering the nostrils
  • to filter dust, bacteria, and other foreign matter from the air using the mucous membrane and its hairs. The mucus collects any dirt and bacteria and prevents it from passing into the lungs. The cilia push the mucus into the throat. It is then swallowed and travels to the stomach where any bacteria are neutralised by gastric acids.

Locate the nasal cavity

Nasal Cavity (Nasal fossa)

It is a large air filled space above and behind the nose in the middle of the face.

Each cavity is the continuation of one of the two nostrils.

  • Nasal Cavity

Identify the parts of Pharynx

Pharynx

Once air has been filtered, moistened and warmed in the nose it travels to the pharynx, a tube which leads from the back of the nose and mouth and divides into the oesophagus (posteriorly) and larynx (anteriorly). It works as part of both the digestive and respiratory systems.

Structure
The pharynx is about 12.5cm long and made of muscular and fibrous tissue. At the back of the section of the pharynx which connects to the nose are small masses of lymphoid tissue which form the pharyngeal tonsils, or adenoids.

Like the palatine tonsils (at the junction of the mouth and throat) the pharyngeal tonsils filter bacteria.

Function
It acts as an air passage and also warms and moistens the air.

  • Nasopharynx
  • Oropharynx
  • Laryngopharynx

What is another name for the throat?

Larynx 

The thyroid cartilage at the top of the larynx, which is larger in men than in women, forms the Adam’s apple which is often visible in the throat.

Structure:
The larynx is a tube positioned between the tongue at the back of the mouth and the trachea (the tube leading to the lungs). It is made of rings of cartilage, attached to each other by membranes and ligaments.

Function:
The larynx is a passageway for air between the pharynx and trachea. It filters bacteria, helps in voice production and warms and moistens the air.

  • larynx
  • epiglottis
  • pharynx
  • bronchioles

What trachea is made up of mainly?

Trachea

Structure:
The trachea is a continuation of the larynx. It is a tube about 10cm long which runs from the front of the neck to the chest where it divides into two bronchi, tubes which lead to the lungs.

The trachea is made of incomplete rings of hyaline cartilage (anteriorly) and involuntary muscle and connective tissue (posteriorly). 

Function:
The trachea is a passageway for air between the larynx and bronchi. The goblet secretory cells in the lining secrete mucus which collects any foreign matter or bacteria and the cilia then push this up to the larynx.

  • spongy tissue
  • mucous membrane
  • cilia
  • cartilage

Which of the following acts as a passageway for air, food and drink?

  • larynx
  • trachea
  • pharynx
  • naso-pharynx

What is the normal breathing rate?

Which of the following is not a function of the respiratory system?

  • producing speech
  • detecting smell
  • regulating blood
  • exchanging oxygen and carbon dioxide

What are the function include in the trachea?

  • Collection of foreign matter or bacteria by the goblet secretory cells
  • Act as passageway between the larynx and pharynx
  • Moisten and warm the air
  • Allow exchange of gases to take place

Part 2 - Describe the function, location and structure of the respiratory system.

Bronchi

Structure:
Bronchi (singular: bronchus) connect the trachea to the lungs. There are two of them, one on the left and one on the right which enter the lungs at the hilum, a concave depression, where they subdivide into different branches for different lobes of the lungs. Like the trachea, they are made of hyaline cartilage, involuntary muscle and connective tissue and are lined with ciliated epithelium.

Function:
To pass air from the trachea into the bronchioles, and thus to the lungs.

Identify the bronchioles

Bronchioles

  • The final and finest tubes in the passage of air from the nose to the lungs are the bronchioles.
  • Made of muscular, fibrous and elastic tissue.
  • They become progressively smaller as they spread further into the lungs until they are no more than a single layer of flattened epithelial cells (just like blood capillaries). 

Function:
Bronchioles take air to the alveoli of the lungs.

  • bronchi
  • bronchioles

What are the tiny air sacs in the lungs which provide a large surface area for diffusion?

Alveoli

  • The exchange of gases in the lungs takes place in tiny sacs called alveoli (singular: alveolus) at the end of the terminal bronchioles.
  • Made of a thin layer of squamous epithelial cells and are surrounded by a capillary network.

Function: To exchange gases between the circulatory and respiratory systems.

The pulmonary artery delivers deoxygenated blood to the capillary network which is then oxygenated by contact with the air in the alveoli.

The oxygenated blood then leaves the lungs via the capillary network and the pulmonary veins and travels to the heart to be pumped around the body.

  • alveoli
  • bronchioles
  • pleura
  • surfactants

Identify the parts of the lungs

Lungs

  • The two lungs are the centre of the respiratory system.
  • It is in these two spongy organs that gases enter and exit the blood.
  • Positioned either side of the heart; the left lung is divided into two lobes, the superior and inferior lobes, whereas the right lung is divided into three, the superior, middle and inferior. Lobes are subdivided into lobules.
  • Lung tissue is made of bronchioles, alveoli, blood vessels, nerves, connective tissue and elastic tissue. They are covered in a special membrane called the pleura.

Function: lungs allow the exchange of gases into and out of the blood.

  • Left Lung
  • Right Lung
  • Middle Lobe

Ribs cage

Function: Provide a moveable cage to enclose and protect the lungs

Identify the muscle layer

Pleura

The pleural cavity is a serous membrane that surrounds each lung.

It has two layers:

  • Visceral layer(Inner) sticks to the lung tissue and covers the surface.
  • Parietal layer(outer) sticks to the chest wall and the top of the diaphragm.

The two layers are separated by a space called the pleural cavity which is filled with a serous fluid.

Function: the pleural cavity prevents friction between the two layers during respiration.

  • Visceral Pleura
  • Parietal Pleura
  • Pleural Cavity

Diaphragm

  • A large muscle, positioned between the chest and abdomen and separates them from each other.
  • Made of a central sheet of tendon with muscle fibres towards the edges and it has three origins –
  • Posterior, lateral and anterior. When relaxed it is a dome shape; when contracted it flattens out.

Functions:

1. Inspiration/inhalation: when the diaphragm contracts, it flattens out and since it forms the bottom of the chest cavity, this cavity then increases in size and volume. This lowers the pressure inside the chest. Air is thus sucked in because the pressure is lower inside the body than outside.

2. Expiration/exhalation: when the diaphragm relaxes it becomes a dome shape and pushes up the chest cavity, thus reducing the cavity’s size and volume and increasing the pressure. Air rushes out because the pressure is lower outside.

3. Helps with expulsive body actions:

  • micturition (urine excretion)
  • defecation (faeces expulsion)
  • parturition (giving birth)

The process of inspiration is consist of?

Intercostal Muscles

These muscles aid the diaphragm in respiration.

During inspiration, the external intercostal muscles contract at the same time as the diaphragm, lifting the rib cage up and outwards. The flattened and lowered diaphragm and the raised ribs cause an increase in the size of the chest cavity.

During expiration, the external intercostals relax allowing the ribs to fall down and inwards, helping to decrease the size of the chest cavity. Nerve impulses delivered by the intercostal nerves tell the muscles when to contract and relax.

  • combined relaxation of the diaphragm and internal intercostals
  • combined relaxation of the diaphragm and external intercostals
  • combined contraction of the diaphragm and internal intercostals
  • combined contraction of the diaphragm and external intercostals

What is the part of the respiratory system extending from the larynx to the upper chest?

  • larynx
  • bronchi
  • trachea
  • pharynx

Respiratory system

Which of the following is the function of the Pleural cavity?

  • the exchange of gases into and out of the blood
  • take air to the alveoli of the lungs
  • prevents friction between the two layers during respiration
  • protect the lungs

What is the common name for windpipe?

  • trachea
  • pharynx
  • larynx
  • bronchi

Revision

Which of the following acts as a passageway for air, food and drink?

  • larynx
  • pharynx
  • naso-pharynx
  • trachea

What is another name for the throat?

  • larynx
  • epiglottis
  • pharynx
  • bronchioles

What is the normal breathing rate?

Which of the following is not a function of the respiratory system?

  • producing speech
  • regulating blood
  • exchanging oxygen and carbon dioxide
  • detecting smell

What are the function include in the trachea?

  • Collection of foreign matter or bacteria by the goblet secretory cells
  • Act as passageway between the larynx and pharynx
  • Moisten and warm the air
  • Allow exchange of gases to take place

What is the common name for windpipe?

  • trachea
  • pharynx
  • larynx
  • bronchi

What are the tiny air sacs in the lungs which provide a large surface area for diffusion?

  • bronchioles
  • surfactants
  • alveoli
  • pleura

What is the part of the respiratory system extending from the larynx to the upper chest?

  • trachea
  • pharynx
  • bronchi
  • larynx

Which of the following is the function of the Pleural cavity?

  • the exchange of gases into and out of the blood
  • protect the lungs
  • take air to the alveoli of the lungs
  • prevents friction between the two layers during respiration